Neck injuries, such as whiplash injury, are prevalent in our society. Although the exact number of whiplash injuries varies from one country to another, it is estimated that the incidence of whiplash injury is approximately 1 in 1000 people in western society. Bogduk et al., Pain, 1994, 58, 283. Whiplash injury is clinically defined as hyperextensionhyperflexion injury of the neck.
In almost all cases, whiplash injury is a result of motor vehicle accidents (MVA). It has been shown that the head is subject to marked rotational acceleration in the first 25 msec after the impact, followed by a reversal of the direction of acceleration as extension occurs. It is estimated that in a rear-end collision of an automobile at a moderate impact speed of 20 miles per hour (mph), the human head reaches a peak negative acceleration of 12 g, i.e., 12 times the gravitational force, and at an impact speed of 40 mph, the human head is subject to negative acceleration of 46 g during extension. Without being bound by any particular theory, it is believed that the neck dissipates force through shear and then torque which exceeds the tolerance levels of bone, muscle and ligament, leading to neck injury. The muscles that normally control the direction and amplitude of motion do not have time to respond to the forces applied to them in an MVA.
The primary symptoms of whiplash injury is either dull or a sharp pain over the back of the neck with associated neck stiffness or restricted movement. This pain is exacerbated by movement. In addition, some suffer headaches, visual disturbances, dizziness, weakness, paresthesia (tingling and numbness sensations), and/or cognitive difficulties as well as other physical and psychological problems.
The majority of whiplash injury patients recover within the first 2-3 months. However, it is estimated that between 14 and 42% of patients with whiplash injuries suffer chronic neck pain and 10% will have pain indefinitely. The economic impact related to WAD is significant due to medical costs and loss of productivity in many patients.
Currently, a variety of methods are used to treat whiplash injuries. One of the treatment methods is cervical epidural steroid injections, which can be hazardous, and some studies have shown that it is ineffective. Another method is drug therapy using analgesics, antiinflammatories or antidepressants. Medication can reduce the pain and/or inflammation but do not address any specific cause of pain. In addition, there is always the dangers of potential harmful side effects from the medication.
One study has shown that compared to rest and wearing a cervical collar, physiotherapy provided significant improvements in cervical movement and pain after 8 weeks. Mealy et al., Br. Med. J., 1986, 292, 656. Other studies have shown that a home exercise program was just as effective as out-patient physiotherapy. McKinney et al., Arch. Emerg. Med., 1989, 6, 27.
Physiotherapy of WAD involves several different techniques, one of which is stretching neck muscles and monitoring the progress of the patient's motion. Such physiotherapy is conducted by a therapist manually manipulating the head and neck of a patient. Typically, no apparatus is used for this treatment. Current methods of monitoring the progress of patients are time-consuming and subject to significant variability from one therapist to another. In addition, the expense and current limitations in health care plans to pay for physical therapy restricts the access of patients to therapists.
Therefore, there is a need for an apparatus for moving neck muscles to stretch and/or strengthen neck muscles which can be used directly by a patient. There is also a need for a simple method of monitoring the progress of a patient's cervical range of motion that can be performed by the patient.